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International Journal of Bioprinting Bacteriorhodopsin-embedded hydrogel device

Figure 1. Schematics of fabrication, characterization, and application of bacteriorhodopsin (br)-embedded hydrogel construct. (A) Schematics of the
fabrication process of the br-embedded hydrogel construct. Alginate sodium, gelatin, and br solution were mixed at 45°C to ensure thorough blending. The
mixed material was then loaded into the nozzle of a 3D printer and cooled to 21°C, which is close to the sol–gel transformation temperature. The substrate
was cooled to 11°C to initiate thermal crosslinking of gelatin, and the printed structure was immersed in a CaCl solution to further ionic crosslink sodium
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alginate. The dual-crosslinking procedure ensures a stable structure and excellent printability. (B) The setup for photoelectrochemical characterization of
br-embedded hydrogel. A microscope objective was connected to a 543 nm laser generator to illuminate the hydrogel. The surface of the bottom and the
top indium tin oxide (ITO) glass were connected to the electrochemical workstation for data acquisition: 1: electrochemical workstation; 2: ITO glass; 3:
br-embedded construct; 4: objective reflector; 5: charge-coupled device (CCD) camera; 6: laser generator. (C) Schematics of the pattern recognition setup
utilizing the photoelectrical properties of br-embedded hydrogel. The input pattern was pixelized to a 5 × 5 grid, and each line consisting of 5 pixels was
encoded to a specific waveform, which was generated through the arbitrary wave generator and transmitted to the temporal modulation of the laser. The
photoelectric response of br-embedded hydrogel corresponding to the modulated laser was then recorded and decoded to an output pattern that stores the
pixelized information of light intensity of the input pattern.

intensity served as the continuous-wave light source, and material (1×: 100 µL in 700 µL; 2×: 200 µL in 700 µL; 3×:
a green laser generator (λ = 543 nm; Yuanming Laser 300 µL in 700 µL; 4×: 400 µL in 700 µL) and then fabricated
Technology, China) was used as the monochromatic light onto an ITO glass substrate. The photoelectrical response
source (Figure 1B). Light intensity was measured using was subsequently measured for different concentrations of
a spectrometer (HP330; Duotone Cloud, China). For br under the same light-intensity conditions.
photoelectrochemical tests, the photocurrent of the hydrogel
construct was recorded employing the i-t mode (sensitivity: 2.4. Pattern recognition
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10 , sampling rate: 50 Hz). Additionally, the linear sweep Temporal pattern recognition was accomplished
voltammetry tests were conducted in both dark and light by encoding pixelized images into time-modulated
illumination conditions (voltage range: 0–0.2 V). Hydrogel illumination and decoding photocurrent responses. An
constructs with varying br concentrations were prepared arbitrary waveform generator (AWG; SDG 1022X; Siglent,
by adjusting the volume of br suspension in the printing China) was configured to produce square waves and

Volume 10 Issue 6 (2024) 519 doi: 10.36922/ijb.4454